“Muscarinic Receptor Antagonists: From Pharmacology to Folklore: Discovering Medications that Effectively Treat COPD and Asthma”

Abstract

Acetylcholine is released into M3 muscarinic receptors by parasympathetic neurons, which give them dominating control over the smooth muscle of the airways in the lungs. Anticholinergic medications that inhibit muscarinic receptors have been used to treat respiratory disorders for more than 2,000 years. Clinical outcomes for antimuscarinic medications in asthma were inconsistent, despite pharmacologic data suggesting that they should be quite effective. As a result, the use of muscarinic antagonists decreased after β-adrenergic receptor agonists were found to be effective. Numerous reasons, such as undesirable side effects (which might range from dry mouth to coma) and the identification of other muscarinic receptor subtypes in the lungs that occasionally have conflicting effects, contribute to the lack of efficacy of muscarinic antagonists. Possibly the most significant issue is inefficient dosing as a result of poorly understood variations in administration routes is no reliable method for determining if antagonists block receptors that acetylcholine stimulates physically. Asthma and chronic obstructive pulmonary disease seem to respond well to the development of newer muscarinic receptor antagonists that address the issues of side effects and receptor specificity.